In the late 1980's some car manufacturers started to use a new tough urethane based primer for their paint systems. Sanding this new primer with abrasive sheet material of the type comprising abrasive coated on a non porous flexible backing sheet (e.g., "Stick-it" gold coat abrasive sold by Minnesota Mining and Manufacturing Company, St. Paul, Minn.) caused excessive loading of the abrasive with removed primer thereby shortening abrasive life. An abrasive sheet material comprising porous screen cloth coated with abrasive and sold by Minnesota Mining and Manufacturing Company under the trade name "Wetordry Fabricut" abrasive has been found to work well to abrade the new urethane based primer without loading, and provides the further advantage that both major surfaces were coated with abrasive and can be used to thereby further extend its useful life. The abrasive coated screen cloth, however, can not be adhered to a back up pad with pressure sensitive adhesive which was commonly used to attach abrasive sheet material of the type comprising abrasive coated on a non porous backing sheet.
While the art describes many back up pads that employ many different attachment structures to attach an abrasive sheet along a support surface without the use of pressure sensitive adhesive (e.g., see U.S. Pat. Nos. 734,954; 1,559,906; 1,710,308; 1,782,577; 2,256,098; 2,493,852; 2,724,936 and 4,202,139), known back up pads are not suitable for manual use to press the abrasive coated screen cloth against the new urethane based primer on curved surfaces such as are commonly found on automobiles, and/or the means for attaching abrasive sheets to known back up pads requires that too large a portion of the abrasive be engaged and thus never used in the abrading process which is wasteful of the abrasive.